SUBSTANCE THAT TURNS MUSCLE TO BONE USED FOR DENTAL DISEASE

In a small study of dental disease in baboons, Johns Hopkins and South African researchers have discovered that a substance that turns muscle into bone healed not only the jawbone but also repaired damaged connective tissue around teeth. The unanticipated finding suggests that the substance may be used to heal some gum and other dental diseases in people.

"It's a fringe benefit for something already very positive," says A. Hari Reddi, Ph.D., a professor of orthopedic research and biological chemistry at Hopkins. "Because of the graying of America,' there will be an increasing amount of problems with bones, cartilage, tendons and ligaments. Our goal is to find factors that stimulate healing, repair and regeneration of these musculoskeletal and dental tissues."

Reddi will present results of the multicenter study at a program titled "Molecular Medicine Enters the Mouth" from 2:30 p.m. to 5:30 p.m. on Feb. 10 at the American Association for the Advancement of Science's annual meeting in Baltimore. Reddi's co-investigator is Ugo Ripamonti, M.D., of Witwatersrand University in Johannesburg, South Africa.

Researchers surgically removed bone and periodontal tissue around the teeth of 12 baboons and filled the openings with bone morphogenic proteins (BMPs), a family of proteins that promote bone growth with collagen, the body's major structural protein and a key part of bones and connective tissues. The BMPs caused new growth in the jawbones, the original goal of the study, but also regenerated ligaments and cementum, the connective tissues that cover the roots of teeth and attach them to the jawbone, says Reddi.

Within three years, BMPs may be used in clinical trials against periodontal diseases, which affect the tissues supporting the teeth. BMPs currently are being used in clinical trials for shattered bones that are not healing properly, as scientists continue to explore the molecular and cellular mechanisms of fracture healing. It may be several years before the substance is used routinely for bone regeneration in humans, but it could apply to a wide range of problems, including skull and facial repairs, osteoporosis, arthritis, reconstructive surgery and sports injuries, says Reddi, a pioneer in bone cell biology.

Bone-healing proteins have been investigated since 1945 for their power to turn soft muscle tissue into bones, but it was not until the late 1980s that a substance called osteogenin was isolated, purified and cloned by Reddi and his colleagues at the National Institutes of Health. Osteogenin, along with other types of BMPs, are normal proteins found in small amounts in bones of humans and other mammals.